Lots of ways.Maybe it's not the "universe" that grants the PC the ability...but under the 2024 rules, it's certainly not a patron either.... So how do you exactly get it? (From an in-world perspective, not a meta perspective)
Here's three:
* third level gives you the benefits of a patron -- you can have one before then, but they haven't noticed you yet. You've sold your soul, or whatever, and got the introductory benefits. So you begin adventuring and eventually merit the attention of your patron, who starts to give you the flavoured abilities that mark you as belonging to It.
* you are stealing magic: you've never trained formally, but you've found a way to tap into a divine being's power and they haven't noticed yet. At third level, then, you finally do get noticed, or your ability to steal their power increases beyond a surface level, and you start to benefit the rich vein. (This works particularly well for a patron of an opposing alignment).
* Or (for pact of the Chain) you capture a sprite (or pseudodragon or quasit or whatever) and it convinces you that there's more power to be had, if only do this...
Honestly, I prefer moving the patron choice to level three because it makes much better sense of Warlock dips: I can see someone "dabbling"with an otherworldly patron, but the full commitment comes with three levels. That's when you commit. I mean really, who is selling their soul for the ability to cast cantrips?